Judy Meyer, President, University of Georgia, Athens, Georgia
Gordon Orians, President-Elect, University of Washington, Seattle, Washington
James Brown, Second Pres.-Elect, University of New Mexico, Albuquerque,
New Mexico
Jerry Franklin, Past President, University of Washington, Seattle, Washington
Robert Colwell, Vice President, University of Connecticut, Storrs, Connecticut
Robert Peet, Secretary, University of North Carolina, Chapel Hill, North
Carolina
Nancy Huntly, Secretary-Elect, Idaho State University, Pocatello, Idaho
Louis Pitelka, Treasurer, Electric Power Research Institute, Palo Alto,
Californiap

Recommended Citation:
Carroll, R., et al. 1996. Strengthening the Use of Science in Achieving
the Goals of the Endangered Species Act: An Assessment by the Ecological
Society of America. Ecological Applications 6(1): 1-11.

The Ecological Society of America is the nation's leading professional
society of ecologists representing 7,500 ecological researchers in the United
States, Canada, Mexico and 62 other nations. Founded in 1915, ESA seeks to
promote the responsible application of ecological principles to the solution
of environmental problems through ESA reports, journals, research and expert
testimony to Congress.

In March of 1992, then President of the Ecological Society of
America, H. Ronald Pulliam, established an Ecological Society of America ad
hoc Committee on Endangered Species. The primary charge to this committee, made
up of nine distinguished ecologists, was to produce a report addressing the
ecological issues relevant to reauthorization of the Endangered Species Act.
The Society's goal in this endeavor was to provide legislators with scientifically
credible information.

The Ecological Society of America has produced other reports focusing
on possible ecological consequences of the release of genetically modified organisms,
delineation of wetlands, and ecological research priorities. These reports have
been favorably received and viewed as credible because of the Ecological Society's
reputation and because the reports focused on science in a policy context.

Strengthening the Use of Science in Achieving
the Goals of the
Endangered Species Act

Strengthening the Use of Science in Achieving
the Goals of the
Endangered Species Act

EXECUTIVE SUMMARY

By enacting the Endangered Species Act of 1973, Congress established a national
commitment to preserve the Nation's biological resources for the benefit of
the American public. The Endangered Species Act sets out a series of steps for
determining whether a species is at risk of extinction, removing the major causes
of its endangerment, and returning the species to a viable state. The Act specifies
all the steps, procedures, and mechanisms to accomplish its goals. Scientific
information is needed for implementing each of these procedures, but the Act
itself provides little guidance as to how to use science to achieve the goals
of the Act.

Therefore, the Ecological Society of America undertook an analysis of how scientific
information could be used more effectively to assist in the preservation of
the Nation's biological resources. This report concludes that:

The 1973 Endangered
Species Act is a powerful and sensible way to protect biological diversity,
and contains the procedures and mechanisms with which to achieve this goal.

On the basis of science, the most important priorities to use in deciding
which candidate species to list are: (1) number of other species that will benefit from the listing;
(2)

ecological role of the species;
(3)
the organism's recovery potential; and
(4)
its taxonomic distinctness.

Formal Population Viability Analysis offers a method to identify how a species'
survival potential can be maximized in the least controversial manner.

The
likelihood of restoring the viability of an endangered species is enhanced when: recovery plans seek to achieve a population distributed in suitable habitats
across the landscape; and these plans are developed and implemented expeditiously.

"...to
provide a means whereby the ecosystems upon which endangered species and threatened
species depend may be conserved. ...to provide a program for the conservation
of such endangered species and threatened species." ...to take such steps as
may be appropriate to achieve the purposes of the treaties and conventions..."
(Endangered Species Act 1988).

By enacting the Endangered Species Act of 1973, Congress, on behalf of the
American people, established a national goal and commitment to protect the Nation's
biological resources. The Act establishes the form and sequence for the process
of providing federal protection, from listing threatened and endangered species
to the implementation of their recovery. The Act is a powerful and sensible
way to protect biological diversity that specifies the procedures and mechanisms
to achieve that goal. However, the original legislation and subsequent amendments
to the Act do not explicitly specify how science will be used to carry out the
legislative mandate. Instead, the manner in which scientific knowledge is to
be used is largely left to the discretion of the implementing agencies, the
United States Fish and Wildlife Service and National Marine Fisheries Service.

The goals of the Act are to identify species that are at risk of extinction,
to implement a process for reducing that risk by limiting additional sources of
jeopardy, and to develop and implement a recovery program. The process is
flexible and can be applied to individual species or to groups of species that
share an ecosystem or management area. If the valuable scientific knowledge
that has accumulated over the past several decades of analytical ecological
research is used to the fullest extent, the Act can become an even more
powerful tool in achieving the societal goals for which it was enacted.

The Act has improved the status of some species, such as the California sea
otter, peregrine falcon, American alligator, whooping crane, and bald eagle.
Nevertheless, each year, many more species are added to the list of endangered
species than are successfully recovered and removed from the list. Despite
being protected, some species are becoming extinct. Currently 955 species in
the U.S. are on the list of endangered and threatened species; only slightly
more than half of them have approved recovery plans (Department of the Interior
1995).

Given this growing list of threatened and endangered species and the limited
success in recovery of endangered species, the Ecological Society of America
undertook an analysis of the Endangered Species Act, with the objective of
assessing how the Act could be made more effective through better use of
scientific information. The nation's biological diversity has great economic,
aesthetic, and spiritual value. Modern society draws upon biological diversity
as a source of medicines, fiber, food, as sources of genes for future
incorporation into crop plants, and for uses we cannot predict. The extensive
services that natural ecosystems provide, such as cleansing of air and water,
control of erosion, and stabilization of climate, depend in part on the
richness of species in those systems. Therefore, the Ecological Society's
analysis accepts and supports the goals and objectives of preserving the
biological heritage of the United States and explores how science can be used
more effectively than it has in the past to enhance the achievement of those
goals.

II. THE IMPLEMENTATION PROCESSES OF THE
ENDANGERED SPECIES ACT

The Endangered Species Act sets out a series of steps for determining whether
a species is at risk of extinction, removing the major causes of its endangerment,
and returning the species to a viable state. The major stages in this process
are:
(1) listing a species as threatened or endangered,
(2) designating the habitat that is critical for survival of the species,
(3)providing immediate protection and prohibition of acts that would further
jeopardize the species, (4) developing and implementing recovery plans, and
(5) delisting the species once it has been restored to a viable state.
Scientific information must be used at all of these stages if an accurate
initial assessment and a successful recovery program are to be achieved.

The process of listing a species includes a series of steps that begins with
a decision to propose a species as a candidate for protection and culminates in
one of three outcomes: rejection of the claim for protection; inclusion of the
species under federal protection as either an endangered or threatened species;
or placing the species in an ill-defined category, known as "warranted, but
precluded." Although decisions on status of species designated "warranted, but
precluded" are to be made within a 12 month finding period, since 1982, 114
species have remained in this category for two or more years. Fifty-six have
been in this category for at least 8 years (GAO 1992).

Once a species is listed, the Endangered Species Act requires the designation
of "critical habitat." In the legislative language, "critical habitat" is
defined as the minimal area that is needed to supply the species with its
immediate survival needs. The Endangered Species Act also provides immediate
protection to a species when it is listed as threatened or endangered. Section 7 of the Act requires all federal agencies to ensure that any actions
they authorize, fund, or carry out do not jeopardize the continued existence
of any listed species or adversely modify its habitat. Thus, every federal agency
must examine whether any action it proposes to carry out might adversely affect
a listed species and these assessments must be scrutinized and evaluated by
the Fish and Wildlife Service or the National Marine Fisheries Service. Scrutiny
occurs through a process known as "formal consultation" and ends with a written
"biological opinion" containing the service's views. These opinions are not
legally binding on the other federal agency but federal agencies are reluctant
to proceed with a project in the face of a jeopardy opinion because the probability
that a citizen suit will be brought against the action is very high.In such
suits, jeopardy opinions are given considerable weight by the courts. Formal
consultations serve other purposes in addition to making jeopardy determinations.
They also search for reasonable alternatives or adjustments to the proposed
action that could avoid jeopardizing a listed species.

Section 7 also deals with incidental take, which is defined as a taking of
a listed species that is incidental to, and not the primary purpose of, otherwise
lawful activities. The term "take" refers to many possible perturbations to
the species, including "harm, harass, kill, wound, catch," etc, all of which
are prohibited under the Act unless authorized by a permit, an incidental take
statement, or a special rule. Incidental take has been interpreted to include
harm to the habitat of a species as well as direct harm to the species itself,
and this interpretation has been upheld in a 1995 Supreme Court decision. From
a scientific standpoint, degradation or destruction of the habitat of a species
can be at least as harmful to the survival of the species as direct injury to
an individual of the species. In 1982 Congress amended the Act to provide mechanisms for regulating incidental
take on non-federal land. Those procedures are now found in section 10(a)(1)(B).
Persons applying for an incidental take permit under Section 10(a)(1)(B) must
submit a "Habitat Conservation Plan" or HPC along with other materials attendant
to their permit application.

In the case of Section 7, "harm" is defined as
an action that significantly reduces both the survival and recovery of a species.
Similarly, in the definition of harmful destruction of critical habitat, a jeopardy
ruling requires that both the survival and recovery of a species be affected.
Many actions slow a recovery process but it is difficult to show unambiguously
that an action threatens the survival of a species (Rohlf 1989). When a species
is listed, the Endangered Species Act requires that a recovery plan be developed.
The ultimate goal of the recovery plan is to improve the status of the species
in its natural habitat to such a degree that it can be delisted. However, by
the time a species becomes eligible for listing, its habitat is often destroyed
or badly degraded, the population is decimated, and its genetic diversity seriously
eroded. Additional delays in developing and implementing recovery plans further
imperil the species. In practice, recovery plans are often not developed for
years, if at all. Through 1991, 61% of the listed species had approved recovery
plans but, of the more than 200 species without recovery plans, more than half
had been listed for three or more years (GAO 1992). The recovery of species
under these circumstances is one of the greatest challenges to the application
of ecological science.

In addition to being delayed, recovery plans often have weak goals. A review
of the 314 approved recovery plans for threatened and endangered species that
were approved by the U.S. Fish and Wildlife Service and the National Marine
Fisheries Service as of mid 1991, found that population goals were often no
higher than existing population densities at the time of listing (Tear et al.
1993). More than half of the vertebrates would remain in serious risk of
extinction even if they met the population targets in their recovery plans. In
some cases, habitat destruction was so severe that the recovery plans had
little chance of success. The reviewers concluded that, "Recovery plans all too
often "manage for extinction" rather than for survival" (Tear et al. 1993).

The ultimate goal of the Endangered Species Act is to restore populations so
that they no longer are threatened with extinction. When that state is reached,
the Act provides for delisting of the species.

III. THE ROLE OF SCIENCE IN THE ENDANGERED SPECIES ACT

Scientific information is needed for implementing all of the processes
specified in the Endangered Species Act. The more high quality science is used,
the more effectively and more efficiently the Act can achieve the important
goals society has asked it to accomplish.

A. Use of Science in the Listing Process

Listing a species as threatened or endangered is the first step in conferring
legal protection. It is the conclusion to a decision-making process that draws
heavily on ecological science, particularly for assessing the level of risk to
a species and developing priorities for listing.

Species are proposed
for protection because they are thought to be in danger of extinction or at
risk of becoming endangered with extinction. For species deserving protection,
delaying the decision to provide protection and recovery will bring most of
these vulnerable species even closer to the brink of extinction, restrict the
options available for achieving recovery, and increase the eventual cost of the
recovery process. Therefore, streamlining the listing process can increase the
effectiveness of the Act in achieving its goals and potentially reduce the
total costs of doing so.

There is no scientific reason why listing, which is an administrative
decision based on the available information, should require much time or agency
resources. The uncertainty that may result from sparse information is part of
the risk that is evaluated during the listing process. Adding independent peer
review or other administrative processes to the listing process would
unnecessarily lengthen the time to make a listing decision without providing
any substantial benefits. The major problem with the listing process has been its slowness, not inadequacy
of the quality of the listing decisions.

1. Which Biological Units Should be Listed?

In the language of the Act, a "species" is taken to include any subspecies of
fish or wildlife (including invertebrates such as insects, crustaceans, and
mollusks) or plant (including fungi). For vertebrates, any distinct population
segment of a species, that is one with unique morphological features or genetic
traits, qualifies as a species. How distinct is distinct enough must be judged
on a case-by-case basis. The meaning of "species" in the language of the Act
is, therefore, somewhat imprecise, but the wording recognizes that a species is
made up of an assemblage of individuals that collectively express genetic,
morphological, and behavioral variation, and that this variation is the basis
of evolutionary change and adaptation.

The scientific justification for extending protection to distinct population
segments of species is that genetic diversity provides the raw material for
adaptation of a species to changing conditions. A wide geographic range
decreases the likelihood that a catastrophic event such as wildfire, disease,
or alien species introduction could wipe out an entire species. The capacity to respond to environmental change through ecological and evolutionary
processes is enhanced by large population size, extended geographical distribution
(including spatial structure among its populations), and intraspecific genetic
diversity. Therefore, because loss of specific population segments can contribute
to the decline of a population and increase the probability of its extinction,
protection of population segments is biologically appropriate.

The National
Marine Fisheries Service has introduced the concept of an "evolutionarily significant
unit" to better define and identify distinct population segments. An evolutionarily
significant unit is a population that is reproductively isolated from other
populations of the same species, which therefore represents an important part
of the evolutionary history and future evolutionary potential of the species.
For example, the species of Pacific salmon are subdivided into many distinct
spawning runs that are evolutionarily significant units of central importance
for the future survival and evolution of the species (Waples 1991).

New species often arise when genes from two species combine and the number
of chromosomes is increased, a process called polyploidy. Polyploidy has given
rise to many species of plants and some animals, including trout and salmon.
Hybrid populations may play unique ecological roles and may stimulate evolutionary
processes. For example, hybrid populations of plants sometimes provide opportunities
for increased speciation among herbivorous insects (Bush 1975). The biological
processes that produce these genetic mixtures are natural components in the
larger processes of speciation and evolution. For these reasons, it is scientifically
appropriate to protect species of hybrid origin.

2. Science and Listing Priorities.

Currently more than 3,000 species are "Candidates" for listing under the Endangered
Species Act, including more than 2,000 vascular plants, 200 mammals, and 750
insects. This large number of candidate species greatly exceeds the capacity of the
Fish and Wildlife Service and National Marine Fisheries Service to evaluate
and propose species for listing as threatened or endangered. In recent years,
about 100 species have been listed annually.

The scarcity of resources available
for listing species requires agencies to make choices about how those resources
can best be allocated to meet the objectives of the Endangered Species Act.
In the 1970s and 1980s, the FWS developed several different schemes for setting
priorities for listing species. These priority systems incorporated such criteria
as: magnitude and imminence of threat, availability of information, taxonomic
distinctness of the species, recovery potential, and population status. The current scheme, adopted in 1983, establishes priorities for listing based
on three criteria:
(1) Magnitude of threat,
(2) immediacy of threat, and(3)
taxonomic status (the greater the evolutionary distinctness of a taxon,
the higher its priority). A fourth criterion--recovery potential--is included in setting priorities for
the development of recovery plans.

This system of priority-setting has the advantage of being relatively simple.
It uses information that is available for most species, and employs criteria
that can be evaluated relatively objectively (Tobin 1990). However, it does
not take full advantage of ecological knowledge that could better guide limited
resources. From an ecological perspective, three attributes should be considered
in a determination of listing priorities:

Inclusive benefits. Will the habitat managed on its behalf
benefit other species, especially species that are listed or are candidates
for listing?

Given the limited resources available for endangered species
protection, giving high priority to species that serve as protective "umbrellas"
for other species makes good ecological sense. For example, the Florida Scrub
Jay (Aphelocoma coerulescens coerulescens) is restricted to scrub oak
habitats on the Florida peninsula. Many rare species of reptiles, insects, and
plants inhabit, and are restricted to, those scrub habitats. Many of them
benefit from the land that is managed for the protection of the jay.
Similarly, many but not all species requiring old-growth temperate rain forest
will benefit if sufficient spotted owl habitat is protected.

The umbrella
species approach must be used carefully because every acre of land or body of
water will contain large numbers of species. Thus, virtually any organism
could be considered an umbrella species at some scale. Moreover, an important
fact about endangered species is that they rarely have exactly the same
requirements. Therefore, even when a suitable umbrella species exists, the
ecological needs of other community members must also be considered. The most
useful umbrella species are ones whose habitats harbor numerous endemic, rare
species. Thus, umbrella species should be given priority for listing in
proportion to the number of other endemic, rare species that co-occur with
them.

Ecological role. Does the species play an especially important
role in the ecosystem in which it lives? Do other species depend on it for
their survival? Will its loss substantially alter the functioning of the ecosystem?

Keystone species--an organism whose impact on its community or ecosystem is
large, and disproportionately large relative to its abundance (Power and Mills
1995)--merit special attention in the listing process. Unfortunately, determining
which species are keystone and which are not is difficult because a species'
importance in an ecosystem is not necessarily proportional to its size, abundance,
or charisma. Tiny fig wasps and African elephants are both keystone species.

Taxonomic distinctness. How evolutionarily distinct is
the taxon in question? On scientific grounds, the more evolutionarily distinct
an organism is, the higher should be its priority for protection. All things
being equal, therefore, saving the sole surviving member of a genus may have
a higher priority than saving an imperiled species within a large genus that
contains many other species. Similarly, protecting full species would normally
be given a higher priority than protecting subspecies and populations (Vane-Wright,
Humphries, and Williams 1991).

Species also have important scientific, aesthetic,
and social values, but, given the paucity of information about most species,
priorities are difficult to assign using those values. Therefore, provisionally it seems scientifically reasonable to give high priority
to species immediately threatened with extinction, to umbrella species, and
to taxonomically unique species. Existing priorities for listing also could
be modified by including considerations of inclusive benefits and ecological
role. For example, among current high priority species (species and monotypic
genera facing high magnitude imminent threats), those providing more inclusive
benefits or playing more important ecological roles should be given higher priority.

B. The Use of Science to Establish Recovery Priorities

The immediate consequence
of listing a species under the Endangered Species Act is to trigger a series
of processes that can recover the species and enable it to be delisted. Recovery
is much more complex and difficult than listing, and development of recovery
plans usually requires the generation of substantial new information in addition
to the evaluation of existing information.

1. Science and Critical Habitat Designation.

Once a species is listed, the
Endangered Species Act requires the designation of "critical habitat." Because
loss of habitat is the cause of endangerment of most species, designation and
preservation of habitat is a vital part of Endangered Species Act procedures.
Because recovery is a long-term, not a short-term process, and the goal of the
Act is to preserve species in perpetuity, enough habitat must be preserved to
allow the species to survive in the long term. But how long is long term and
how much is enough?

The scientific procedure used to estimate the probability of survival of a
population for a specified period of time is known as Population Viability Analysis,
or PVA (Shaffer 1990). Although there is no strict definition of what is or
is not included, each PVA should include an analysis of the best available information
on the focal species. Most PVA analyses combine data from field studies with
simulation modeling of the possible impacts of various extinction factors (Doak
et al. 1994, Murphy et al. 1990; Menges 1990; Stacey and Taper 1992).

The details
of a PVA analysis depend on the characteristics of the focal species (Murphy
et al.1990). Species with low population densities and small geographic ranges (most endangered
large vertebrates, for example) and small geographic ranges (many plants) require
a PVA that includes analysis of the genetic and demographic factors that affect
small populations. Smaller organisms, such as most threatened invertebrates,
frequently are restricted to a few habitat patches, but within those patches
they often have high population densities. For these species PVAs need to analyze
environmental uncertainty and the probability of local catastrophic factors.
PVAs for plants require different emphases than PVAs for animal species because
individual plants may survive for many years even if they are not reproducing
successfully (Schemske et al. 1994). A PVA for a migratory species may also have to incorporate explicitly how its
populations are linked through migration and how its population dynamics are
influenced by processes operating at a landscape scale.

A good PVA addresses
the issue of how long is long enough by attempting to answer the following questions:
Is the population viable in both the short term and the long term? What factors
are currently putting it at risk? How can these risks be reduced or eliminated
so that the population can both survive and recover? There are no clear criteria for determining how long is long enough, but in
practice a minimum viable population (MVP) is typically defined as one that
has a 90% probability of persisting for 200 years.

A PVA was performed on the
Acorn Woodpecker (Melanerpes formicivorus), a non-endangered bird that lives
in small, isolated populations in the oak woodlands of western United States
and Mexico (Stacey and Taper 1992). A simulation model showed that most of these
populations would become extinct within 20 years if they were totally isolated
from one another. However, with a small amount of migration among populations,
the model indicated that most of the populations would last more than 1,000
years. Historical records indicate that local populations of these woodpeckers
have survived more than 70 years, suggesting that migration must be important
in maintaining them.

Population viability can seldom be assessed by focusing on a single patch of
suitable habitat and the organisms living in it. Most organisms live in islands
of suitable habitat, among which there is an exchange of individuals, embedded
in a larger landscape. Because the populations in the various patches are linked
by the movement of dispersing individuals, the fate of the populations is interconnected.
Studies of population viability of many organisms will therefore need to consider
the importance of factors that link subpopulations. The whole set of populations of a species that are linked through migration
in a habitat mosaic is known as a "metapopulation."

The long-term survival of metapopulations can be strongly affected by the spatial and temporal distribution
of suitable and unsuitable habitat patches. Populations living in high quality
habitats (referred to as "source" habitats) have birth rates greater than death
rates; the excess individuals may migrate into lower quality habitats ("sink"
habitats) where birth rates are less than death rates. The viability of metapopulations
depends on the existence of sufficient high quality habitats, but a large
fraction of the individuals may live in the sub-optimal habitats (Pulliam
1994). To determine the critical habitat needs of such species requires
identification of source and sink habitats, which may be difficult.

Not every rare and endangered species is patchily distributed in a spatially
structured habitat mosaic. Some live in just a few continuous or in completely
isolated habitats. Some have a "core-satellite" structure in which one very
large population (the core) determines the population dynamics in the small
(satellite) populations. Nonetheless, because many species do depend on source and sink habitats, every
protection and recovery plan for species should investigate the need to include

spatially distributed populations that are linked through migration, and

special protection of the most stable, high quality habitats.

For some species, the designated critical habitat may need to include more
than habitat actually occupied by the species. This is especially true in cases
where the quality of critical habitat is dependent on land use in the surrounding
area (e.g., Noss 1983, Turner et al. 1995). Although this is a general concern,
the need for a larger scale of focus in the designation of critical habitat
is most apparent for aquatic species. If the watershed that supplies river and
lake ecosystems is degraded, the critical habitat needed by the endangered species
may also be destroyed.

The data available for most candidate species will not allow a precise
determination of MVP or critical habitat. From a scientific standpoint, the
resolution to this problem is to designate interim critical habitat at the time
a species is listed and to designate long-term critical habitat as part of the
recovery plan. A monitoring and research program that generates information
about the requirements of the species needs to be established. Procedures
should allow for revisions of critical habitat designations if suggested by
additional information.

The Endangered Species Act, although it focuses on species as the objects of
concern, clearly recognizes that preservation of the ecosystems upon which
endangered and threatened species depend is a necessary component of the
recovery process. This feature was written into the Act because loss of habitat is by far the
most important cause of endangerment of species in the United States. A particular
habitat type may be lost by destruction or conversion to other habitat types
unsuitable for the species that live in it. A habitat may also be degraded by
pollutants without being otherwise altered. The fact that habitat preservation
is the most important element of most recovery plans creates several possibilities
for using scientific information in more comprehensive ways.

Because many species
that depend upon a habitat that has been greatly reduced in area or otherwise
degraded are similarly affected by losses of that habitat, a number of listed
or candidate species are likely to live in the same habitat. In a recent out-of-
court settlement, the United States Fish and Wildlife Service formalized a commitment
to emphasize multiple species listings and proposals that address entire ecosystems
(Jaffe 1993), a result that demonstrates the appropriateness and legality of multispecies processes under the existing Act. Managing for multiple species within a single management area focuses efforts
on recovery of threatened species while simultaneously directing attention to
broader issues of habitat quality and quantity.

Multispecies planning differs
from ecosystem management because its focus is still on species. Nonetheless,
a multispecies approach to preservation plans inevitably directs attention to
habitats and ecosystems. Habitat-based packages that combine the listing efforts
for many species have the potential to eliminate unnecessary duplication of
efforts and to prevent species from becoming threatened in the first place. Thus, a likely consequence of more extensive use of a habitat approach is that
the need to invoke the Endangered Species Act will arise less frequently than
it does now.

2. Use of Science in Protection and Prohibition against Jeopardy

Section 7 of the Endangered Species Act provides immediate protection to a species
when it is listed as threatened or endangered. The analyses leading to no jeopardy
or jeopardy opinions, together with the search for nonjeopardizing alternatives,
offer considerable scope for the use of ecological knowledge. Jeopardy opinions,
as well as non-jeopardy opinions, may become irrelevant unless they are regularly
updated to reflect changed circumstances and new information. Ideally,
recovery plans should provide tangible standards or yardsticks for judging
whether particular federal actions satisfy Section 7. Recovery teams could play
a useful role in this regard, by advising the Fish and Wildlife Service and
National Marine Fisheries Service with respect to particular consultations.

The likelihood that a species will become extinct does not increase uniformly
as its population declines. Rather, thresholds at which the probability of
extinction rises rapidly are the rule. The importance of thresholds needs to be
taken into consideration during evaluations of "incidental take." A determination of the consequences of incidental take should be based on the
effect it would have on the process of restoring the species to its safe
minimum population density. Thus, if the damage from incidental take was
estimated to cause a 5% loss in the population size of a listed species, the
consequences of that additional mortality on the likelihood of extinction could
be shown explicitly through a population viability analysis. Furthermore, because PVAs
emphasize the principal causes of a species' vulnerability to extinction,
alternatives to the proposed action, such as mitigation, could be considered
and evaluated.

In the broadest sense, the implementation of the Endangered Species Act is a
process of risk assessment and risk management. Assessing risk of extinction,
which is the function of the listing process, is a purely biological procedure.
Any associated economic consequences that might arise from designating an
imperiled species as endangered or threatened are not, and should not be, part
of the risk assessment equation. However, in the "risk management" phase which
follows the listing of a species, the Act appropriately permits the
consideration of possible economic costs and infringement of personal property
rights in the designation of critical habitat, in the determination of
allowable harm to the species (takings and jeopardy), and in the development
and implementation of recovery plans.

Formal population viability analyses could assist this process because a given
level of probability of survival for a specified time period might well be achieved
in many different ways, some of which would impose more restrictions on private
land owners than others. PVAs could identify those options that would achieve
maximum protection while reducing costs and lowering political controversy.

Science can play a valuable role in stimulating the consideration and evaluation
of a wide range of actions at the time a federal action is contemplated. All
too often formal consultations are limited to a consideration of a small number
of options that are proposed as ways of avoiding harm to some listed species.
Impacts of the options on other species often are not considered, and options
that might be better than those being evaluated are rarely discussed.
Broadening the range of options being considered increases the up-front costs,
but if superior options are identified and eventually implemented, long-term
costs may be reduced substantially.

Biologists in the agencies responsible for implementing the Endangered
Species Act generally try to use the best scientific information and methods
available. Failure to use the best available information and methods is
generally due to inadequate budgets and overworked staff. Incorporating greater
scientific rigor into the recovery process will result in initially higher
costs because better methods for identifying species at risk, formal population
viability analysis, and adequate habitat restoration and recovery programs all
require greater investment. However, if the best available science is used
consistently, common patterns will emerge and species protection and recovery
will become more cost-effective. In other words, as experience is gained, each
new case can build upon the results of previous cases. Rather than treating
each new species to be protected as a totally novel situation, more powerful
general rules can be applied and the process thereby simplified. The rapidly
growing field of Conservation Biology, with its own professional, scientific
Society of Conservation Biology, is already providing some of the needed
information.

Furthermore, the development of general rules that are well-grounded in both
experience and theory, can be useful in predicting which kinds of species and
circumstances are likely to be sensitive to disturbance from human activities
and in evaluating acceptable alternatives to the proposed actions.

In many regions of the United States, particularly the West Coast and the
Southeast, threatened and endangered species occur on private land, and the
concurrence of landowners will be required to protect the habitat of the
species and to implement species recovery plans. This situation generates a
need for interdisciplinary studies by resource economists and ecologists. The
objectives of these studies should be the development of models and field
approaches for determining least-cost solutions to habitat protection.

Furthermore,
the pathways to these solutions should be "user-friendly" so that landowners
can identify with the process. As an example of this approach, Liu (1992)
developed a model for pine plantation management that shows the effects of
different tree harvesting patterns and rotation lengths on the population size
of Bachman's sparrow. This model shows how the real opportunity costs of forgoing the most profitable
management plan are related to the probability of survival of Bachman's sparrow.

3. Use of Science in Development and Implementation of Recovery Plans.

When
a species is listed, the Endangered Species Act requires that a recovery plan
be developed. The ultimate goal of the recovery plan is to recover the species
in its natural habitat to such a degree that it can be delisted. However, by
the time a species becomes eligible for listing, its habitat is often destroyed
or badly degraded, the population is decimated, and its genetic diversity seriously
eroded. Therefore, scientific information is especially needed for setting population
goals, captive breeding and release, and habitat protection and restoration.

Setting Goals for Recovery. The first goal of a recovery plan is to stop
the population decline before the species is on the brink of extinction. If
listing as an endangered species was warranted, a recovery plan usually must
aim for a population size significantly greater than the size at the time
of listing. A good recovery plan for an endangered species typically has three
goals for achieving viable populations. First, it calls for the establishment
of multiple populations, distributed so that migration among them is possible,
so that a single catastrophic event cannot wipe out the whole species. Second,
it moves to stop known threats that guarantee the continued decline and eventual
extinction of the population. Third, it plans for achieving annual population
growth rates greater than zero, which will increase the size of populations
to levels where demographic and normal environmental uncertainties are less
threatening.
Doing so requires careful analysis of the habitat requirements of the species
and the distribution of suitable habitats in the landscape.

Analyses to determine
long-term recovery goals and programs for attaining them are a vital component
of recovery plans. However, because their development may require considerable
time, short-term interim goals may be needed to prevent the species from becoming
extinct while long-term plans are being developed. Interim population goals
should be biologically attainable during the first years of the recovery process.
One exception to setting larger recovery goals is if a species were naturally
restricted to a very small area. In such a case, it might be listed as endangered,
but recovery might require only removal of the threat it faces, in the restricted
area.

General tentative guidelines for establishing viable population sizes
are available (e.g., Gilpin and Soul‚ 1987) but these target population goals
are no more than rough estimates and should not be viewed as substitutes for
a more thorough analysis.Interim populations goals need to be flexible and readily adjustable. For
example, an appropriate goal over a three-year period for a rapidly reproducing
species might be the establishment of three semi-isolated populations with
a combined population size greater than three times the original population
size at the time of listing. For species with low reproductive rates, an increase
in the size of the population of that magnitude within a few years may not
be possible. Although interim goals are necessary, population viability analyses
should begin immediately so that long-term population goals can be established
and the most important factors threatening the species can be identified in
a timely manner.

It is always tempting to set as a recovery goal a population
of a specific size and spatial distribution. For many species, however, a
goal of a relatively constant population is biologically unrealistic and probably
intrinsically undesirable. Many species live in unstable, fluctuating environments,
and their populations have historically fluctuated together with the states
of their environments. For example, many species depend upon habitats that
are maintained by periodic fires, droughts, or floods. Populations of such
species inevitably fluctuate greatly in space and time. Realistic management
goals must reflect this biological reality.

For example, the 1986 recovery
plan for the Snail Kite (Rostrhamus sociabilis) in the Florida Everglades
sets an interim population goal for reclassification from endangered to threatened
of an "annual average of 650 birds for a ten-year period with annual population
declines of less than 10% of the average."
However, kite numbers vary, and have probably always varied, considerably
according to surface water conditions, which change dramatically along with
drought cycles in southern Florida. Achieving a population having the stability
outlined in the interim population goal is probably unattainable. Also, attempting
to achieve great population stability might well lead to management interventions
that in the long term reduce the quality of kite habitat and, hence, the long-term
viability of the population. However, it is generally useful to establish
critical minimum population sizes below which extinction probabilities become
unacceptably high even if they are sustained for only short time periods.

Captive-breeding and Translocation. Reintroduction of captive- bred individuals
and translocation of individuals between populations are often components
of recovery plans. However, captive breeding programs are expensive, can save
only one species at a time, and can be used only rarely because available
facilities are limited. Also, because unexpected undesirable consequences
may arise, captive propagation programs are risky. Deleterious genes may arise
in captivity, or individuals released in areas other than the ones from which
they or their parents were taken may not be adapted to the environments in
which they are released.
Diseases may be carried by the reintroduced individuals. Behavioral traits
may develop in captivity that prevent individuals from functioning appropriately
in nature. For these reasons, careful attention must be given to the sources
of individuals for release to the wild and their treatment in captivity. Similar
considerations apply to introductions of plants propagated in botanical gardens
and other artificial environments.

There is also a danger that wild populations
may be depleted to obtain individuals for captive breeding programs, although
in special instances, such as occurred in the case of the California Condor
in the 1980s, capture of all remaining individuals in the wild population
may be warranted. Captive breeding programs may draw attention away from the
need to protect and restore habitats for the focal species. Successful species
recovery plans ultimately depend on adequate amounts of protected habitat.
Captive-release or translocation programs of native populations, although
important, cannot substitute for the failure to protect or restore natural
habitat (Povilitis 1990).
The danger is illustrated by the Gila topminnow, which was reclassified from
endangered to threatened because artificial habitats were successfully restocked
with captive-bred fish. However, the natural habitat continued to degrade
from the effects of alien mosquitofish and agricultural water withdrawals
(Simons et al.1989). The continuing loss of the fish's natural habitat makes
its survival in artificial pools increasingly improbable.

Habitat Protection and Restoration. Often the best approach for restoring
habitat is to control the source of the degradation and let nature take its
course. Unfortunately, habitats are often very badly degraded or too small
to contain adequate heterogeneity and natural disturbance regimes. In those
situations, active management is needed to restore and maintain the habitat.
Habitat restoration and ecological management are critically important to
the species recovery process. Methods to restore and manage habitats are not
yet well-developed, but the field of Restoration Ecology is growing rapidly
(Jordan, Gilpin, and Aber 1987; MacMahon and Jordan 1994).
Its practitioners increasingly should be able to provide insights and guidance
for restoration efforts in a variety of habitats.

Critical components in the
development of a recovery plan for a listed species are determination of the
current extent of its suitable habitat, assessment of the quality of the remaining
habitat, and establishment of priorities for the areas to be targeted for
restoration efforts. Restoration efforts can also be designed to test hypotheses
about how the ecological community in question functions and the roles of
the various species that might be reintroduced as part of the restoration
project.
Ideally, several different restoration projects should be initiated
in different patches of a given habitat so that more than one hypothesis about
the functioning of the community can be tested. Such a procedure would increase
the probability that the results of specific restoration projects are generalizable
to other habitats, while increasing the speed of restoration of the habitat
in question by identifying more promising restoration techniques.

C. Delisting, the Ultimate Goal of the Endangered Species Act

Delisting is the ultimate objective of the Act. Measures of progress toward
this goal include prevention of extinction and slowing the rate of population
decline. The criteria for delisting should be established early in the
recovery process, and they should be based on sound biological information.
As discussed previously, delisting criteria should be consistent with natural
fluctuations in the habitats supporting a species.

However, results obtained as recovery was underway may require
modifications in the original criteria as better information about habitat
requirements and population dynamics of the species become available.

IV. CONCLUSIONS

Protection is not afforded to species and their habitats under the Endangered
Species Act until species are already threatened with extinction. By that time,
both the range of a species and its total population size are likely to have
been seriously reduced. Recovery under these circumstances is likely to require
major habitat restoration efforts and, possibly, captive propagation. These
activities are more expensive and are less likely to be successful, the later
in the decline of the population they are initiated. Therefore, the goals of
the Endangered Species Act are more likely to be achieved, and to be realized
at lower total cost, if preservation of biological diversity were approached
in a more proactive manner.

The most important elements of a proactive approach would be to identify habitats
and biological communities that are being seriously reduced in area or are being
otherwise degraded and then to establish policies that prevent further losses
of those habitats and restore degraded parts of them. Such an approach could
not replace a species- by-species analysis because not all species are threatened
by habitat loss and threatened species require different habitat types. Nonetheless,
a habitat-based, proactive approach should greatly reduce the number of species
that would need to be considered for listing.In addition, a proactive
approach, by identifying habitats experiencing or likely to experience serious
losses would allow federal agencies to initiate preservation plans while more
options are available than will be present at such time when particular species
would become candidates for listing. Habitat-and ecosystem-level planning can
be accomplished under the existing Endangered Species Act, particularly through
the use of critical habitat designations for already listed 'umbrella species."
For both scientific and economic reasons, such proactive planning needs to be
greatly increased. The establishment of the National Biological Service is an
important step in developing the data needed for proactive, habitat and
ecosystem level planning.

However, if the protection of habitats and ecosystems is to become an
important means for conserving biological diversity, some important questions
need to be addressed. Ecosystems are not closed systems; they are dependent on outside conditions.
Ecosystems and habitats can be recognized at many scales. Aquatic ecosystems
may range in size and complexity from small ponds to the Great Lakes. Determining
the most appropriate scales for protecting them will require considerable information
and complex biological judgments. New legislation for ecosystem-level protection,
designed to complement and strengthen current legislation, could greatly assist
protecting the nation's renewable natural resources, including its rich biological
diversity. An ecosystem approach could help to reverse the slide towards extinction
by preventing habitat degradation. The Endangered Species Act would then function as the safety net for those
species whose survival cannot be guaranteed within the protected ecosystems.